1. Field of the Invention
The present invention relates to a cutting tool in which an exchangeable cutting head having a cutting portion is attached removably to a tool body.
This application is based on and claims priority from Japanese Patent Application No. 2009-079852, filed on Mar. 27, 2009 and Japanese Patent Application No. 2009-286638, filed on Dec. 17, 2009, the contents of which are incorporated herein by reference.
2. Background Art
Conventionally, a cutting tool in which an exchangeable cutting head is attached removably to a tool body is known.
In the cutting tool having the exchangeable cutting head, the exchangeable cutting head includes a cutting head body having a cutting portion and a connection member that is provided at a rear-end of the cutting head body and has a head screw section.
In addition, the tool body has a mounting hole formed at the tool body and a female screw section formed at the mounting hole.
In the foregoing cutting tool having the exchangeable cutting head, the exchangeable cutting head is inserted into the mounting hole of the tool body, and the head screw section of the connection member is screwed into the female screw section of the mounting hole of the tool body.
As an example, a cutting head body and a connection member are formed so as to be integrated in one body in a powder metallurgy process, and an exchangeable cutting head made of a hard material is disclosed in Japanese Unexamined Patent Application, First Publication No. H07-164234.
In the structure, a head screw section of the above-described connection member is screwed into a female screw section formed at a mounting hole of a tool body, and the cutting head body is thereby detachably attached to the tool body.
In addition, as an example, an exchangeable cutting head in which a cutting head body and a connection member are removably coupled each other is disclosed in Japanese Unexamined Patent Application, First Publication No. 2004-98272.
In the structure, in a state where the cutting head body is connected with the connection member, a head screw section of the connection member and a female screw section formed at a mounting hole of a tool body are screwed together, and the exchangeable cutting head is attached removably to the tool body.
In a method for connecting the cutting head body with the connection member, an end portion of a hook section is formed at one of the cutting head body and the connection member, a hook hole of the hook section is formed at the other of the cutting head body and the connection member, the end portion is inserted into and passed through the hook hole.
Subsequently, the cutting head body is rotated in relative to the connection member in a circumferential direction, the cutting head body is connected with the connection member.
In the above-described cutting tool having the exchangeable cutting head, it is preferable that the cutting head body be made of a hard material in order to improve sharpness or abrasion resistance in a machining process.
On the other hand, when the head screw section of the connection member is screwed in the tool body, since stress is generated at a screw thread, it is preferable that the head screw section of the cutting head be made of a material with a high level of toughness.
However, in the above-described exchangeable cutting head used in the cutting tool having the exchangeable cutting head disclosed in Japanese Unexamined Patent Application, First Publication No. H07-164234, the cutting head body and the connection member are formed of a hard material so as to be integrated in one body, and there is a drawback in that a screw thread thereof is easily fractured when stress occurs at the head screw section.
In addition, due to concentrated stress at a root portion of the screw, there is a drawback in that the screw may break.
In order to avoid the foregoing drawback, it is necessary to machine each screw thread in a particular form to spread stress generated in the screw thread, therefore a manufacturing cost increases.
In addition, in the exchangeable cutting head of the cutting tool having the exchangeable cutting head disclosed in Japanese Unexamined Patent Application, First Publication No. 2004-98272, since the cutting head body can be separated from the connection member, it is possible to form each of the cutting head body and the connection member by use of a different material.
However, a configuration of the hook section or the hook hole is complicated, and a manufacturing cost for molding the hook section or the hook hole increases.
In addition, in a step for attaching the cutting head body to the tool body, it is necessary to initially combine the cutting head body with the connection member, and there is a problem in that an hour of labor is required.